Chapter 19 Flashcards
Immediate hypersensitivity is an immune reaction
triggered by?
antigen binding to IgE pre-bound to
mast cells, which leads to the release of inflammatory mediators
The steps in the development of immediate hypersensitivity are what?
exposure to an antigen (allergen)
that stimulates TH2 responses and IgE production,
binding of the IgE to Fcε receptors on mast cells,
cross-linking of the IgE and the Fcε receptors by
the allergen, activation of mast cells, and release
of mediators.
Individuals susceptible to immediate hypersensitivity reactions are called what?
atopic and often have
more IgE in the blood and more IgE-specific Fc
receptors per mast cell than do nonatopic individuals
IgE synthesis is induced by exposure to what?
antigen and TH2 cytokines, particularly IL-4
Mast cells are derived from bone marrow precursors that mature in tissues. They express what?
highaffinity receptors for IgE (FcεRI) and contain
cytoplasmic granules in which are stored various
inflammatory mediators
Subsets of mast cells,
including mucosal and connective tissue mast
cells, may produce what?
different mediators. Basophils
are a type of circulating granulocyte that expresses
high-affinity Fcε receptors and contains granules
with contents similar to mast cells
Eosinophils are a special class of granulocyte; they are recruited into inflammatory reactions by what?
chemokines and IL-4 and are activated by IL-5
Eosinophils are effector cells that are involved in what?
in killing
parasites. In allergic reactions, eosinophils contribute to tissue injury
On binding of antigen to IgE on the surface of mast
cells or basophils, the high-affinity Fcε receptors
become what?
cross-linked and activate intracellular
second messengers that lead to granule release and
new synthesis of mediators
Activated mast cells
and basophils produce three important classes of
mediators:
biogenic amines, such as histamine;
lipid mediators, such as prostaglandins, leukotrienes, and PAF; and cytokines, such as TNF, IL-4,
IL-13, and IL-5.
Biogenic amines and lipid mediators cause ?
the
rapid vascular and smooth muscle reactions of
immediate hypersensitivity, such as vasodilation,
vascular leakage and edema, bronchoconstriction,
and gut hypermotility
Cytokines released by mast
cells and TH2 cells mediate?
the late-phase reaction,
which is an inflammatory reaction involving neutrophil and eosinophil infiltration.
Various organs show distinct forms of immediate
hypersensitivity involving different mediators and
target cell types. The most severe form is what?
a systemic reaction called anaphylactic shock. Asthma
is a manifestation of immediate hypersensitivity
and late-phase reactions in the lung. Allergic rhinitis (hay fever) is the most common allergic
disease of the upper respiratory tract
Drug therapy is aimed at what?
inhibiting mast cell mediator production and at blocking or counteracting
the effects of released mediators on target organs
what is the goal of immunotherapy?
is to prevent or to
reduce TH2 cell responses to specific allergens and
the production of IgE
